Detectable warnings

ABSTRACT

A detectable warning tile which aims to solve the problem of buckling and cracking associated with different thermal expansion properties of the tile and the substrate in which it is installed. Said tile is provided with underside flanges on only some of the outermost vertical surface of the tile. The tile need not be a quadrilateral, the tile may have more or fewer than fours edges.

RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 61/542,532 filed 3 Oct. 2011.

SUMMARY

Methods, systems and devices for detectable warnings are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic picture of a replaceable detectable warning tilewith a protective upper lip and lower flanges on two opposing edges butnot on the other two edges.

FIG. 1B is a close up schematic picture of the same tile depicted inFIG. 1A.

FIG. 1C is a schematic picture of the same tile depicted in FIG. 1Alooking along the long axis of the tile.

FIG. 1D is a schematic picture of the same tile depicted in FIG. 1Alooking from underneath.

FIG. 2 is a photograph of an example of a tile including a flexiblegrommet surrounding a fastener.

FIG. 3 is a series of schematic drawings of a tile assembly including anisolation tray.

FIG. 4A is a schematic picture of a replaceable detectable warning tilewith a protective upper lip designed to promote self-cleaning.

FIG. 4B is a schematic picture of the same tile depicted in FIG. 4Alooking along the long axis of the tile to emphasize the triangularshape of the upper lip.

FIG. 4C is a schematic picture of the same tile depicted in FIG. 4A.

FIG. 5A is a schematic picture of a replaceable detectable warning tilewith features designed to allow venting from below to above the tile.

FIG. 5B is a close up schematic picture of the tile depicted in FIG. 5A.

FIG. 5C is a schematic of a screw with ribs on the underside of thescrew head.

FIG. 5D is a schematic of an anchor that allows venting.

DETAILED DESCRIPTION

FIGS. 1-4 show detectable warning tiles. The upper surface of such atile includes detectable warnings, in this case truncated domes asspecified by Americans with Disabilities Act Accessibility Guidelines.The tile is designed to warn the visually impaired that they areapproaching a hazard, and so can be installed, for example, at the edgeof train platform or at a curb ramp where a pedestrian walkway meets aroad.

The tiles of FIGS. 1-4 are designed to be installed in wet concrete. Ineach case, the unit is assembled by attaching anchors to the tile usingfasteners, e.g., screws, as shown. Once the anchors are attached to thetile, the entire unit may be pressed into wet concrete so that somesurface of the tile is flush with the surrounding walking surface, whilethe truncated domes protrude upward to allow for tactile detectability.In this way, the truncated domes will protrude above the walking surfaceso as to provide a tactile warning to visually impaired pedestrians.

The anchors are formed with a bottom portion that is wider that at leastsome other portion of the anchor. Once the concrete cures and hardens,the wider, lower portion will be locked in place vertically by thehardened concrete. In some cases, anchors are formed so that thehardened concrete will lock the anchor in place horizontally as well. Asshown in the figures, some anchors are formed with a polygonal, e.g.,hexagonal, horizontal cross-section. Because this part of the anchor isnot circular, the cured, hardened concrete will prevent the anchor fromspinning about a vertical axis. The anchor may also include verticalprotrusions that similarly prevent the anchor from spinning.

FIGS. 1C and 1D also show a different type of anchor that mimics a ribon the underside of the tile. This rib-anchor is fastened to the tile bymultiple fasteners at different locations unlike the single-fastener,hexagonal anchors also shown. Ribs can be used to provide stiffness orstrength to the tile, and the multi-fastener anchor can mimic thoseeffects.

The tile is attached to the anchors by the fasteners. If the fastenersare removed, the tile can be removed leaving the anchors in place in theconcrete. The tile can be removed because it is shaped or otherwiseformed so that the cured concrete does not lock it in place. To theextent that the tile protrudes downward into the concrete, and to theextent that such downward protrusions vary in width as a function ofheight, the protrusions should be narrower, or at least not broader, thelower they go (except in the isolation tray embodiment described below).

Such replaceable detectable warning tiles can have a number of problemswhich are addressed by inventions disclosed herein.

Preventing Buckling

A first problem is buckling. Because the tile is typically not made outof the same material as the substrate in which it is installed (e.g.,polymer composite tile vs. concrete substrate), the tile and thesubstrate may have different thermal expansion properties. When the tileis installed and the concrete cures, the void in the concrete formed bythe tile will conform to the tile precisely. But as the temperaturevaries, the expansion or contraction of the concrete will change theshape of the void into which the tile must fit. At the same time, thesize of the tile will also change due to thermal expansion, and it willdo so at a different rate than the concrete. If the tile becomes toolarge for the space in the concrete into which the tile must fit, theunit must somehow deform and may buckle.

Similarly, when the tile is installed and the concrete cures, theanchors are aligned with attachment points on the tile where the anchorsare fastened to the tile. As the temperature varies, it is the thermalexpansion of the concrete that determines the location of the locked-inanchors, while the thermal expansion of the tile determines the locationof the attachment points. If the tile and concrete expand at differentrates, the anchors may cease to be well-aligned with their attachmentpoints. This too may cause the tile to buckle.

Generally, buckling may be prevented or reduced by reducing theinteraction of flanges on the tile with the underlying concrete. Inparticular, the FIGS. schematically depict several ways of addressingthe problem of buckling.

FIG. 1A shows schematically a tile with underside flanges on only twoopposing sides, with the other two opposing sides left without anyflange. Some wet-set, replaceable, detectable warning tiles haveunderside flanges on all (typically four) sides of the tile. By leavingsome sides of the tile with no underside flange, buckling may bereduced. In particular, FIG. 1A shows a tile with a long direction,presumably perpendicular to the direction in which pedestrian will walkover the tile, and a short direction, parallel to the direction ofpedestrian traffic. In FIG. 1A, the tile has underside flanges on thelong sides, running perpendicular to the direction pedestrian traffic,and no flanges on the short sides parallel to pedestrian traffic. Asshown in detail in FIG. 1B, the underside flanges are separated by theshorter horizontal dimension of the tile. Longer flanges separated bythe shorter direction of the tile may cause less buckling than shorterflanges separated by the longer direction of the tile. But in eithercase, leaving one or more sides with no flange, may reduce buckling.More generally, a tile may reduce buckling where at least one, in somecases both, of two opposing sides has no flange.

The flanges may extend from the outermost vertical surface of the tileunit, or, as shown, the tile may extend horizontally beyond the flange.The tile need not be rectangular. For example, the tile could have anarcuate shape, or trace out an angular sector of an annulus. The tilealso need not be a quadrilateral, even a curvilinear quadrilateral; thetile may have more than four or fewer than four edges.

Another way of reducing the problem of buckling is to allow the anchorsand/or fasteners to move relative to the tile. Since the anchors arelocked into the concrete, they will necessarily move differently due tothe thermal expansion than the points on tile to which the anchors areattached, e.g., the holes for the fasteners. FIG. 2 shows a flexiblegrommet that fits around the fastener, which, in this case, is a screw.The fastener is rigidly fixed to the anchor, but because the grommet isflexible and compressible, the fastener can move relative to the tilewithout forcing the tile to deform; the grommet is deformed instead.Some previous detectable warning tiles have used fasteners with headsthat are designed to mate closely with the hole in the tile, e.g., ascrew with a countersink head that mates with a conical hole in thetile. In employing the present idea, it is important that the fastenerdoes not mate so closely with the tile that it becomes impossible forthe fastener to move relative to the tile. Thus, the screw shown in FIG.2 is a flat-head screw and the tile is cut to leave room for the head ofthe screw to move relative to the tile.

Alternatively, the fastener may be fixed to the tile, but allowed tomove slightly relative to the anchor. The anchor may be made of someflexible material that allows the fastener to move slightly with thetile while the anchor stays fixed in the concrete.

In any case, the amount of relative thermal expansion or contractionallowed may be the amount of expansion or contraction associated with aspecific change in temperature of the tile, for example 1, 2, 3, 4, 5,10, 15, 20, 25, 30, 40 or 50 degrees centigrade.

FIG. 3 shows yet another way of addressing the problem of buckling, byinstalling the tile in an isolation tray. In this embodiment, a tray isaffixed to the tile. The fasteners pass through the tile, through thetray and then into the anchors. The isolation tray is larger than thetile, leaving room for the tile to expand and contract horizontallyinside the tray. An exposed gap between the tray and the tile can besealed, for example with a flexible caulking that allows for expansionand contraction of the tile while preventing debris from falling intothe tray. The presence of the tray leaves a horizontal gap between thetile and the surrounding concrete, allowing the tile to expand andcontract relative to the concrete without buckling. The is alsobeneficial when used with a replaceable tile in that the tray keeps thetile from coming directly in contact with the concrete, making the tileeasier to remove. Moreover, because the tile is not embedded directly inthe concrete, underside protrusions can be any shape, including wider attheir lowest point, without compromising replaceability. The isolationtray may be made from a variety of materials, and in particular, couldbe made from a material whose thermal expansion characteristics mimicthose of concrete.

Protecting Detectable Warnings

A second problem with some detectable warning tiles is damage to thetruncated domes when a snow plow or shovel is scraped across the top ofthe tile. Where detectable warnings protrude above the level of thesurrounding walking surface, a plow or shovel that travels along thewalking surface may shear off or otherwise damage a truncated dome. FIG.1A shows a detectable warning tile with an upward facing lip to addressthis problem. The upper surface of the tile is generally flat,punctuated by truncated domes. The lip protrudes upward from the tile toa greater height than the truncated domes. In this way, the blade of asnow plow or shovel may ride along the upper lip without ever contactingthe truncated domes. Thus the lip protects the truncated domes fromdamage. Where tiles are intended to be installed adjacent to oneanother, the upper lip may extend only along some sides of the tile. Inthat way, an upper lip can be formed around a collection of tiles withno upper lip along the internal seams between tiles. FIG. 1A shows atile with an upper lip along only three of its four sides.

Cleaning

A third problem with some detectable warning tiles is the difficulty ofcleaning the tile. FIG. 4A shows a detectable warning tile designed tobe at least partially self-cleaning. The unit has an upper lip toprotect the detectable warnings from snow plows as described above. Inthis case, the upper lip is broken at locations on the long sides of thetile, near the corner. In this way the upper lip defines one or moreopenings. The upper lip along the long sides of the tile is also widerat the center than at the corners. In FIGS. 4A-4C the long sides of theupper lip have triangular peaks, but many such shapes will suffice. Whensuch a tile is installed on a slope, for example in a curb ramp, or curbcut, with one long side below the other long side, debris will roll orflow down the slope, hit the lip on the lower edge of the tile, thenroll or flow along the sloped lip down to the corner where it can bechanneled away through the break in the lip. In this way, the upper lipcan be shaped to promote self-cleaning when installed on a slope.Although only the downhill side of the tile needs to have toabove-described shape and openings to work as described, the upper lipas shown in FIGS. 4A-4C is symmetrical for ease of installation, so thatthe tile can be installed with either long edge at the top or bottom ofthe slope.

Venting

Wet-set tiles are installed by pressing the tile down into wet concrete.If the tile has downward projections, such as flanges or ribs on theunderside, depending on the geometry of those projections, air may gettrapped between the wet concrete and the tile. A number of differentmechanisms can be used to allow such air to vent from underneath thetile. For example, if the only downward protrusions are flanges on twosides and there are other sides with no flanges, air will escape alongthe sides that have no flange. FIG. 1D shows the underside of a tilewith a series of ribs. Because of the arrangement of the ribs, even whenpressed into wet concrete, the tile creates no isolated pockets of airthat cannot escape via the sides with no flanges.

Venting can also be achieved by leaving room for air to flow around thefasteners. FIG. 5A shows two ways of allowing venting around thefasteners. Detail A of FIG. 5A shows a hole through the tile. Thefastener passes through the hole and attaches to the anchor. As thefastener is tightened in the anchor, the anchor becomes held to thetile. But the hole shown in Detail A is not merely a countersink toallow the screw head to be recessed. The horizontal and verticalsurfaces of the hole include channels that allow air to flow from belowthe tile to above the tile, even when a screw is seated in thecountersink. When the screw is tightened down, it seats against thehorizontal surface of the countersink, leaving channels underneath thescrew that continue to the underside of the tile. This is shown in moredetail in FIG. 5B.

FIG. 5C shows a screw with protruding ribs on the underside of the screwhead. This screw similarly serves to allow venting around the screw frombelow to above the tile. When the screw is tightened down against thetile, the ribs contact the horizontal surface of the countersink,leaving the rest of the screw head removed from the tile. As long as thescrew does not completely fill the through hole and the head does notcompletely fill the countersink, the ribbed screw will thus leaveopenings for air to flow from below the tile to above the tile.

Any arrangement of fastener and through hole that leaves space for airto vent could be effective to allow venting around the fastener.

The fasteners attach to anchors that seat tightly against the undersideof the tile. In order for air to flow around the fastener, the anchorcannot be allowed to completely block the hole. FIG. 5D shows an anchorwith six circular bosses that allow the anchor to stand off from theunderside of the tile even when firmly attached to the tile. An anchorlike the one in FIG. 5D can be used with any combination of fastenersand holes that allows for venting.

We claim:
 1. A detectable warning tile comprising: a body having a firstedge, a second edge, and a third edge; a first flange integral with anddepending from the body, the flange aligned with the first edge; and nointegral flange aligned with the second and third edges.
 2. The tile ofclaim 1 wherein the body further comprises a fourth edge opposed to thesecond edge.
 3. The tile of claim 2 further comprising a second flangeintegral with and depending from the body, the second flange alignedwith the fourth edge.
 4. The tile of either of claim 2 or 3 wherein thefirst and fourth edges are opposed to one another and the second andthird edges are opposed to one another.
 5. The tile of claim of eitherof claim 2 or 3 wherein the first and second edges are opposed to oneanother and the third and fourth edges are opposed to one another. 6.The tile of any of claims 2-5 wherein the body is rectangular.
 7. Adetectable warning tile comprising: a body with a plurality ofattachment points, a plurality of fasteners, and a plurality of anchors;wherein the number of attachment points is equal to the number offasteners and the number of anchors; wherein each fastener is affixed toa single anchor and attaches that anchor to the body at a singleattachment point; and wherein each fastener is attached to the body insuch a way that the body can expand or contract and move each attachmentpoint without moving the each fastener and anchor, and without otherwisedeforming the body.
 8. The tile of claim 7, wherein: the body defines aplurality of through-holes equal to the number of fasteners; eachfastener passes through one through-hole; and the through-holes aresufficiently larger than the fasteners that the body can expand orcontract and move each attachment point without moving the each fastenerand anchor, and without otherwise deforming the body.
 9. The tile ofclaim 8 further comprising a plurality of grommets equal to the numberof fasteners, each grommet positioned within a through-hole andsurrounding a fastener, each grommet being sufficiently deformable toallow the body to expand or contract and move each attachment pointwithout moving each fastener and anchor, and without otherwise deformingthe body.
 10. The tile of any of claims 7-9 wherein each fastener isattached to the body in such a way that the body can expand or contractan amount equal to tile's expansion due to a change in temperature of 20degrees centigrade.
 11. A detectable warning tile comprising: a bodywith a plurality of attachment points, a plurality of fasteners, and aplurality of anchors; wherein the number of attachment points is equalto the number of fasteners and the number of anchors; wherein eachfastener is affixed to a single anchor and attaches that anchor to thebody at a single attachment point in such a way that the body can expandor contract and move each attachment point and fastener without movingthe each anchor, and without otherwise deforming the body.
 12. The tileof claim 11 wherein the anchors are sufficiently deformable that thebody can expand or contract an amount equal to tile's expansion due to achange in temperature of 20 degrees centigrade.
 13. A detectable warningtile assembly comprising: a body, a fastener, an anchor and an isolationtray; wherein the isolation tray is affixed to the body by the fastenerand the anchor; and wherein the body fits within the isolation tray overpredetermined range of temperatures despite thermal expansion orcontraction of the body relative to the tray.
 14. A detectable warningtile comprising: a body having at least one edge and an upper surface; aplurality of detectable warnings on the upper surface; and an upper lipalong the at least one edge; wherein the detectable warnings rise aspecified height off the upper surface, and the upper lip rises agreater height off the upper surface.
 15. The tile of claim 14 whereinthe upper lip is broken so as to define at least one opening in theupper lip.
 16. The tile of claim 15 wherein the upper lip is widest at apoint between two openings and is narrowest where the upper lip definesthe two openings.
 17. A detectable warning tile comprising: a body witha plurality of attachment points and an equal plurality of fasteners;and an anchor attached to the body by each of the plurality offasteners; wherein each of the fasteners attaches the anchor to the bodyat a different one of the plurality of attachment points.
 18. Adetectable warning tile assembly comprising: an anchor, a fastener, anda body defining a through-hole; wherein the fastener passes through thethrough-hole and attaches the anchor to the body; and wherein thethrough-hole, fastener and anchor are sized and shaped such that, whenthe tile assembly is pressed into wet concrete, air can vent from belowto above the body.
 19. The tile of claim 18 wherein the through-holedefines at least one channel sized and shaped so that when the fastenerattaches the anchor to the body, air above the tile is in fluidcommunication with air below the tile through the at least one channel.20. The tile of claim 18 wherein the fastener comprises at least one ribsized and shaped to prevent a surface of the fastener from contactingthe body, so that the fastener and the body define at least one channelthrough which air above the tile is in fluid communication with airbelow the tile.
 21. The tile of claim 18 wherein the anchor comprises atleast one boss sized and shaped to prevent a surface of the anchor fromcontacting the body, so that the anchor and the body define at least onechannel through which air above the tile is in fluid communication withair below the tile.